Method and apparatus for receiving a universal input voltage in a welding, plasma or heating power source

ABSTRACT

A method and apparatus for providing welding type power is disclosed. The power source is capable of receiving any input voltage over a wide range of input voltages and includes an input rectifier that rectifies the ac input into a dc signal. A dc voltage stage converts the dc signal to a desired dc voltage and an inverter inverts the dc signal into a second ac signal. An output transformer receives the second ac signal and provides a third ac signal that has a current magnitude suitable for welding, cutting or induction heating. The welding type current may be rectified and smoothed by an output inductor and an output rectifier. A controller provides control signals to the inverter and a controller power supply can also receive a range of input voltages and provide a control power signal to the controller, and a voltage independent of the input voltage.

FIELD OF THE INVENTION

[0001] This invention generally relates to power sources. Moreparticularly, this invention relates to power sources employed inwelding, cutting and heating applications.

[0002] Power sources typically convert a power input to a necessary ordesirable power output tailored for a specific application. In weldingapplications, power sources typically receive a high voltage alternatingcurrent (VAC) signal and provide a high current output welding signal.Around the world, utility power supplies (sinusoidal line voltages) maybe 200/208V, 230/240V, 380/415V, 460/480V, 500V and 575V. These suppliesmay be either single-phase or three-phase and either 50 or 60 Hz. Otherpower supplies, such as that available in mines or subways, may be dc.Additionally, power may be provided from generators that attempt toprovide power at such voltages and frequencies, or at other voltages andfrequencies, or at dc.

[0003] Welding power sources receive such inputs and produce anapproximately 10-40 volt dc high current welding output. Substantialpower is delivered to a welding arc which generates heat sufficient tomelt metal and to create a weld. Cutting power sources receive suchinputs and produce an approximately 80 volt dc high current cuttingoutput. Induction heating power sources receive such inputs and producean approximately 200 volt ac high current heating output. Becausewelding, heating and cutting require similar high power outputs, weldingtype power source or supply, as used herein, includes welding, plasmaand induction heating power sources and supplies. Welding type power, asused herein, refers to welding, plasma or heating power.

[0004] Given the various utility and generator power inputs it isdesirable for a welding/plasma/heating power supply to be able toreceive any of a wide range of power inputs. Several hurdles must beovercome to allow a power supply to receive multiple input voltages.First, the power circuit must be able to receive the expected voltagemagnitudes and frequencies, yet still provide the desired outputvoltage. Second, the desired control voltage must,-be provided,regardless of the input voltage. Also, when aux power (for tools etc.)is being provided, the desired output voltage and frequency (110V ac at60 Hz, e.g.) must be provided regardless of the input voltage andfrequency.

[0005] Early power supplies overcame these hurdles by having taps ontransformers correspond to each expected voltage. The taps were selectedby the user manually “relinking” the power supply for each inputvoltage. This was time consuming, and required the user open the powersupply. Operating an improperly linked power source could resultimpersonal injury, power source failure or insufficient power.

[0006] A prior art welding source that improved upon manual linkingprovided an automatic linkage. For example, the Miller ElectricAutoLink®, described in U.S. Pat. No. 5,319,533, incorporated herein byreference, tested the input voltage when they are first turned on, andautomatically set the proper linkage for the input voltage sensed. Thepower supply included two inverters connected in parallel (for 230V, forexample) or in series (e.g., for 460V). Such arrangements generallyallow for two voltage connection possibilities. However, the highervoltage must be twice the lower voltage. Thus, such a power sourcecannot be connected to supplies ranging from 230V-460V to 380V-415V or575V.

[0007] Another prior art power supply that was a significant advance inthe ability of a power source to receive a wide range of power isdescribed in U.S. Pat. No. 5,601,741, issued Feb. 11, 1997, onapplication Ser. No. 08/342,378, filed Nov. 18, 1994, entitled MethodAnd Apparatus For Receiving A Universal Input Voltage In A Welding PowerSource, and is owned by the assignee of the present invention. The powersupply described in U.S. Pat. No. 5,601,741 is implemented commerciallyin the Miller Omniline® power supply.

[0008] The welding/plasma/heating power supply of U.S. Pat. No.5,601,741 (incorporated herein by reference), includes an input stage, apreregulator stage, and an output stage. Also, a controller (with apower source) controls the power supply to produce a desired output. Thepower supply for the controller is referred to as an auxiliary powersupply therein. However, the present invention also includes a poweroutput for tools etc that is often referred to as an auxiliary poweroutput. Thus, to avoid confusion, the power output for tools will bereferred to herein as aux power, and the power for the controller willbe referred to herein as control power.

[0009] Generally, the Omniline® input stage receives ac utility orgenerator power, and rectifies that power to provide a first dc signal.The rectified dc signal is provided to the preregulator, which includesa boost converter. The boost converter boosts the rectified signal tocreate a dc bus. The output stage includes an inverter, transformer, andrectifier which create welding, cutting, or heating power (welding typepower) from the bus.

[0010] Because a dc bus is created (by the boost converter) and theninverted to create the output power, the output power voltage andfrequency is independent of the input voltage and frequency. This allowsa wide range of input voltages and input frequencies to be used.

[0011] However, power for the controller is derived by transforming theinput voltage. The control power circuit determines the magnitude of theincoming power, and configures taps on a transformer to obtain thedesired control power. The control power transformer is relatively smallsince the amount of control power needed is relatively small. While awide range of input power are thus acceptable, the input must besufficient that, for a selected tap, the control voltage is acceptable.

[0012] Thus, the Omniline® provided the desired output voltage byinverting a dc bus having a magnitude independent of the input voltage.Also, the Omniline® created control power by selecting taps on atransformer. This allowed a wide range of input voltages to be used, butstill required the input voltage to have an appropriate magnitude forbeing transformed into a control voltage. Additionally, this prior artdid not provide an aux power (for tools), that had a voltage andfrequency independent of the input voltage and frequency.

[0013] Accordingly, a welding power source that may receive any commoninput voltages or frequency is desirable. Preferably, this isaccomplished without the need of any linkages for the welding powerinput and for the control power input. Additionally, it is desirable tohave such a welding power source that produces aux power and weld powerhaving a frequency and voltage independent of the input frequency andvoltage.

SUMMARY OF THE INVENTION

[0014] According to a first aspect of the invention a welding type powersource is capable of receiving a range of input voltages andfrequencies. It includes an input circuit, a preregulator, an outputcircuit, a preregulator controller, and a control power circuit. Theinput circuit receives input power at an input frequency and an inputmagnitude, and provides a signal having a magnitude responsive to theinput magnitude to the preregulator. The preregulator provides a dcsignal having a preregulator magnitude independent of the inputmagnitude to the output circuit. The output circuit provides a weldingtype output power signal having an output frequency independent of theinput frequency and having an output voltage independent of the inputvoltage. The preregulator controller is connected to the preregulator,and receives power from the control power circuit. The control powercircuit derives power from the dc signal and provides control power tothe controller that has a control power magnitude independent of theinput magnitude and a control frequency independent of the inputfrequency.

[0015] The input circuit includes a rectifier in one embodiment.

[0016] The preregulator magnitude is greater than the first magnitude,and the preregulator includes a boost converter in various alternatives.The boost converter may include a slow voltage switched switch and aslow current switched switch.

[0017] The output circuit includes an inverter, which may include aswitched snubber in other alternatives.

[0018] The preregulator magnitude is greater than the control powermagnitude, and/or the control power circuit includes a buck converter inadditional embodiments.

[0019] According to a second aspect of the invention a method ofproviding welding type power from a range of input voltages andfrequencies includes receiving an input power signal having an inputfrequency and an input magnitude. A first signal having a magnituderesponsive to the input magnitude is provided. The first signal isconverted into a dc second signal having a second magnitude independentof the input magnitude. A welding type power signal derived from the dcsecond signal has an output frequency independent of the input frequencyand further has an output voltage independent of the input voltage. Thedc second signal is converted into control power having a control powermagnitude independent of the input magnitude.

[0020] The input signal is rectified in one embodiment.

[0021] The second magnitude is greater than the first magnitude, andconverting the first signal into a dc second signal includes boostconverting the first signal in other embodiments. Boost converting mayinclude slow voltage switching and slow current switching a switch.

[0022] The output power signal is provided by inverting the dc secondsignal, and/or using a switched snubber in various alternatives.

[0023] The second magnitude is greater than the control power magnitude,and/or converting the dc second signal into control power includes buckconverting the dc second signal in additional alternative.

[0024] According to a third aspect of the invention a welding type powersource capable of receiving a range of input voltages and frequenciesincludes a de bus. An output circuit receives the dc bus, and provides awelding type output power signal. The output power is voltage andfrequency independent of the input power. A controller is connected tothe output circuit. Power for the controller comes from the dc bus,through a control power circuit.

[0025] According to a fourth aspect of the invention a method ofproviding welding type power from a range of input voltages andfrequencies includes receiving a dc bus and providing welding type powerat a magnitude independent of the bus magnitude, but derived from the dcbus. The dc bus is also converted into control power whose magnitude isindependent of the dc bus magnitude.

[0026] According to a fifth aspect of the invention a method of startingto provide providing welding type power from a range of input voltagesand frequencies, includes receiving an input power signal and providinga first dc signal at magnitude responsive to the input's magnitude. Asecond dc voltage whose magnitude is less than the first dc magnitude isderived from the first dc magnitude. A control converter is controlledwith the second dc voltage such that the control converter produces acontrol dc voltage. An output converter is controlled with the controldc voltage to produce an output signal.

BRIEF DESCRIPTION OF THE DRAWINGS

[0027]FIG. 1 is a block diagram of a welding power supply constructed inaccordance with the present invention;

[0028]FIG. 2 is a circuit diagram of one embodiment of 20 thepreregulator of FIG. 1;

[0029]FIG. 3 is a circuit diagram of one embodiment of an inverter witha switched snubber used in the output circuit of FIG. 1;

[0030]FIG. 4 is a circuit diagram of one embodiment of the controllerpower circuit and portions of the controller of FIG. 1; and

[0031]FIG. 5 is a circuit diagram of one embodiment of the aux powercircuit and portions of the controller of FIG. 1.

[0032] Before explaining at least one embodiment of the invention indetail it is to be understood that the invention is not limited in itsapplication to the details of construction and the arrangement of thecomponents set forth in the following description or illustrated in thedrawings. The invention is capable of other embodiments or of beingpracticed or carried out in various ways. Also, it is to be understoodthat the phraseology and terminology employed herein is for the purposeof description and should not be regarded as limiting. Like referencenumerals are used to indicate like components.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0033] While the present invention will be illustrated with reference toa particular power supply, having particular components, and used in aparticular environment, it should be understood at the outset that theinvention may also be implemented with other power supplies, components,and used in other environments.

[0034] Referring now to FIG. 1, a welding power source 100 includes aninput circuit 101, a preregulator 102, an output circuit 103, acontroller 104, a controller power supply 105, and an aux power supply106.

[0035] Input circuit 101 receives input utility or generator power, andprovides a signal to preregulator 102. The input is ac, and the inputcircuit includes a rectifier and capacitor bank in the preferredembodiment. Thus, the output of the input circuit is a dc (uni-polar)signal, having a frequency twice that of the input frequency. Inputcircuit 101 is comprised of other components in alternative embodiments.

[0036] Preregulator 102 receives the signal from input circuit 101 andprovides preregulated signal. Preregulator 102 includes a boostconverter and boosts the rectified signal to be a dc bus (about 800 Vdc)in the preferred embodiment. Preregulator 102 is controlled so that,regardless of the input, the dc bus voltage is about 800 V. Thus, themagnitude of the dc bus voltage is independent of input magnitude. (Asused herein a second voltage is independent of first voltage whenmagnitude of the second voltage is controlled to be a value which is notproportional to or a function of the first voltage). Also, the dc busfrequency (substantially zero, but with ripple) is independent of theinput frequency. (As used herein a second voltage is independent offirst voltage when magnitude of the second voltage is controlled to be avalue which is not proportional to or a function of the first voltage).

[0037] Preregulator 102 includes other types of converters, such as aninverter, a series resonant converter, etc., in other embodiments.Converter, as used herein, includes a power circuit that receives orprovides an ac or dc signal, and converts it to the other of an ac or dcsignal, or to a different frequency. Inverter, as used herein, includesa power circuit that receives or provides a dc bus signal that isinverted to be an ac signal.

[0038] If a dc input signal is received, input circuit 101 simply passesthe dc signal to preregulator 102, or is omitted altogether. If the dcinput signal is of a sufficient magnitude, preregulator 102 may passsimply provide the dc input as the dc bus, or be omitted altogether.

[0039] Output circuit 103 receives the dc bus and provides an outputsuitable for welding/heating/cutting. Output circuit 103 includes, inthe preferred embodiment, an inverter, followed by a transformer,followed by a rectifier and an output inductor. The output power is alsofrequency and voltage independent of the dc bus and the input signal.Output circuit 103 is comprised of other components in otherembodiments, and may provide an ac or dc output.

[0040] Controller 104 includes control circuitry similar to that knownin the prior art, and causes the boost and inverter switches to switchin response to feedback and a setpoint (such as 800V for the boostconverter and a user setpoint for the output inverter).

[0041] Control power is provided to the controller by controller powersupply 105. Controller power supply 105 derives power from the output ofpreregulator 102, in the preferred embodiment. Controller power supply105 includes a buck converter that steps down the 800V to 15V dc. Themagnitude and frequency of the output of controller power supply is thusindependent of the dc bus, and the input power. It is easily seen that,once the 800V dc bus is present control power is easily derived from thebus rather than from a control power transformer, any input voltage andfrequency is acceptable. Thus, linking, such as adjusting transformertaps, need not be performed.

[0042] The circuitry that controls preregulator 102, output circuit 103and controller power supply 105 is collectively called controller 104because of the common function (controlling). However, in practice theymay form distinct and remotely located circuits, they may sharecircuitry, they may reside in a common microprocessor or DSP, and theymay share control signals and feedback.

[0043] One potential difficulty at start up is a result of the switchingof the buck converter in controller power supply 105 being controlled bycontroller 104: The 800V dc bus is not created until the controllercauses the boost converter switch to switch on and off, but thecontroller cannot control the switch until it has power, and the powerfor the controller is derived from the dc bus.

[0044] This difficulty is overcome in the preferred embodiment becauseeven before the boost converter begins to switch to create the 800V dcbus, the dc bus will have the same magnitude as the rectified inputvoltage, which is typically at least 110V rms. Since the buck convertersteps down the bus voltage to 15V dc, even a relatively low magnitudeinput voltage (110V ac e.g.) is sufficient to create the controllerpower. Also, control power for the buck converter is derived from afloating 15 volt supply, by bleeding current from the bus.

[0045] The start up sequence will be described in detail below, butgenerally is as follows. At start up the dc bus quickly rises to therectified input voltage, through a precharge resistor. The prechargeresistor is bypassed after the bus is charged. Current bled from the buscharges capacitors which provide power for the buck convertercontroller. The buck converter controller controls the buck converter,causing it to produce 15V dc power for all of controller 104. Controller104 controls the boost converter in preregulator 102 to step up therectified input and produce an 800V dc bus. Thus, the 800V dc bus iscreated, and can provide power to output circuit 103 when the userbegins to weld.

[0046] Additionally, aux power supply 106 includes an inverter, andproduces a synthetic aux power, i.e., a desired output voltage at adesired output frequency (110V ac at 60 Hz, e.g.). Controller 104 alsocontrols aux power supply 106.

[0047] Input circuit 101, preregulator 102, output circuit 103, and theportions of controller 104 that control them, are implemented using thecircuitry shown in U.S. Pat. No. 5,601,741 (and correspond to likenumbered features of the drawings therein) in one embodiment. However, awide variety of circuits may be used to implement this part of thepresent invention, and the details of will not be described in detailherein.

[0048] A particular switching circuit is used for the preregulator inanother embodiment because it provides for efficient slow voltageswitching and slow current switching. This circuit is described inpatent application Ser. No. 09/111,950, filed, Jul. 9, 1998, entitledPower Converter With Low Loss Switching, and owned by the owner of thisinvention. Slow voltage/current transitions or switching (SVT and SCT)as used herein, describe transitions where the voltage or current riseis slowed (rather than held to zero), while the switch turns off or on.

[0049] The circuit used in the preferred embodiment to implementpreregulator 102 is shown in FIG. 2 (along with input circuit 101 andvoltage source 109). The embodiment of FIG. 2 uses a 90-250 volt acpower line as input voltage 109. Input circuit 101 is comprised ofdiodes D60, D70, D80, and D9, which rectify the input voltage to providea single polarity sinusoidal input voltage.

[0050] A power factor correction portion (described below) ofpreregulator 102 functions best when the input, voltage is sinusoidal,although it could be another alternating input. Thus, a small (10 μF)capacitor (not shown) is provided across the input rectifier in oneembodiment to smooth the input line voltage.

[0051] The rectified input voltage is applied to a boost inductor L10(750 μH) which is connected with a boost switch Z1 (preferably an IGBT)to form a boost convertor, An anti-parallel diode D50 is connectedacross switch Z1 to protect switch Z1 during transitions. The portion ofthe circuit which provides the lossless switching includes a snubberinductor L2 (3.9 μH) a pair of capacitors C100 (1 μF) and C200 (0.068μF), and diodes D10, D20, D30, and D40. Switch Z1 is switched in a knownmanner such that the output of preregulator 102 is a desired voltage, nomatter what the input voltage is. The output is provided across acapacitor C50 (2000 μF) that provides a stable voltage source (200 voltsin the preferred embodiment) for the downstream convertor. Also,capacitor C50 prevents the voltage from being dangerously high anddamaging switch Z1.

[0052] The portion of preregulator 102 that provides power factorcorrection is a power factor correction circuit 204 (FIG. 2), andgenerally senses the input voltage waveform, and conforms the shape ofthe current waveform to be that of the line voltage waveform. Thisprovides a power factor of very close to 1, 0.99 in the preferredembodiment. Power factor correction circuit 204 may be implemented usingan integrated circuit, such as a UC3854 or an ML4831, or with discretecomponents, such as those shown in the above-referenced Power ConverterWith Low Loss Switching, incorporated herein by reference.

[0053] Power factor correction circuit 204 receives as inputs the outputvoltage from input circuit 101, the output voltage from preregulator102, and the output current of preregulator 102 (using a CT). Becausethe frequency of preregulator 102 (25 Khz) is much higher than that ofthe line (60 Hz) the pre-regulator current can be made to track theinput line voltage shape by sensing the shape of the input voltage, andcontrolling the input current in response thereto.

[0054] Output circuit 103 can include a conventional inverter, outputtransformer, output rectifiers, and an output-inductor such as in U.S.Pat. No. 5,601,741. However, in one embodiment, the inverter is aswitched snubber, such as that described in Power Converter With LowLoss Switching, and shown in FIG. 3.

[0055] The invertor implemented with a switched snubber includes a dcvoltage source 1501, a pair of switches 1502 and 1504, with a pair ofanti-parallel diodes 1503 and 1505, a pair of capacitors 1507 and 1508(1410 μF), a transformer 1509, a capacitor 1512 (0.099 μF), anoutput-rectifier including diodes 1510 and 1511, and an output inductor1513.

[0056] Capacitor 1512 is switched across transformer 1509 by switches1502 and 1504. Switches 1402 and 1403 are used to soft switch switches1502 and 1504. Switches 1402 and 1403 do not need any special timing,and run with the main clock at effectively 50% duty cycle. For example,switches 1502 and 1402 turn on together, and switch 1502 deliverscurrent to transformer 1509, while switch 1402 does nothing. When switch1502 turns off, switch 1402 remains on, and current is directed throughswitch 1402 and diode 1405 into capacitor 1512, thus giving an SVT (SlowVoltage Transition) turn off. Switch 1402 is turned off after thetransition and diode 1405 prevents the back flow of current fromcapacitor 1512. This occurs in complimentary fashion with switches 1502and 1402 and diode 1405. Thus, this circuit provides full-wavetransformer usage, PWM control, complete capacitor balance control withno extra circuitry, and efficient use of switches with SVT. Analternative embodiment includes using a full bridge version of thesnubber.

[0057] The specific circuitry used to control the switched snubber maybe conventional control circuitry, such as that described in PowerConverter With Low Loss Switching.

[0058] A circuit used to implement controller power supply 105, and aportion of controller 104 that controls controller power supply 105 isshown. Controller power supply 105 includes a buck converter in thepreferred embodiment, and includes a switch 401, a freewheeling diode403 and a buck inductor L1, configured in a conventional buckarrangement, and a resistor 404 (0.5 ohms).

[0059] The circuitry that controls the buck converter (or regulator), inthe preferred embodiment, is also shown on FIG. 4, and is part ofcontroller 104. One skilled in the art will readily recognize that thecontrol circuitry may be located on the same control board as theportion of controller 104 that controls preregulator 102 and outputcircuit 103, or it may be located remotely therefrom, for example on thePC board for controller power supply 105.

[0060] Generally, the buck converter is controlled such that at startupcurrent is bled from the DC bus to charge a capacitor, thus providingsufficient power to turn on and off the buck switch. The voltage acrossthe capacitor is a floating voltage and is sufficient to operate thebuck converter control circuitry. The control circuitry causes the buckswitch to turn on and off repeatedly to create a control power of about15 volts DC. The 15 volts DC is then used to power the remaining controlcircuitry.

[0061] More specifically, when the power supply is turned on the DC buswill have a voltage equal to the peak voltage of the input rectifiedsignal (about 200 volts DC for an input having 140 volts RMS, e.g.).Current bleeds from the bus through a pair of resistors R5 (150 Kohms)and R4 (150 Kohms) to charge a pair of capacitors C5 (0.1 μF) and C2(100 μF). The voltage across capacitors C2 and C5 is called the BUCK-COMand BUCK+15V, and is the floating voltage supply for the circuitry thatcontrols the buck converter, Proper selection of the resistance ofresistors R5 and R4 (and other components described below) determinesthe minimum voltage needed on the dc bus to operate the buck convertercontrol circuitry. In the preferred embodiment the minimum voltage is nohigher than that obtained by rectifying 110V ac power.

[0062] When the voltage across capacitors C5 and C2 reachesapproximately 11.7 volts a switch Q1 turns on, Switch Q1 is used toenable (or disable) the logic or control circuitry for the buckconverter. When the voltage across capacitors C2 and C5 is less thanabout 11.7 volts, then switch Q1 off, and the logic circuitry isdisabled. A resistor R2 (10 Kohms), a resistor R3 (100 Kohms) and azener diode D1 (11 volts) are associated with switch Q1, and create theturn on voltage. Thus, the resistance of resistor R3 also sets theminimum voltage needed to operate the circuitry that controls the buckcontroller.

[0063] The logic circuitry includes a plurality of NAND gates U4A, U4B,U4C, AND U4D, and associated circuitry capacitors C1 (0.1 μF) and C3(0.001 μF), resistors R6 (20 Kohms), R7 (332 Kohms) and R8 (20 Kohms).This circuitry controls a plurality of paralleled NOT gates U3, whoseoutput is the on/off signal to the-base of buck switch 401, through aresistor R12 (10 ohms). The supply voltage for the logic circuitry isthe floating BUCK-COM/BUCK+15V voltage supply.

[0064] When NOT gates U3 output is 1, buck switch 401 is on, and whenNOT gates U3 output is 0, buck switch 401 is off. NOT gates U3 output is1 when their input is 0, which requires both inputs of NAND gate U4D tobe 1.

[0065] At start up, before the bus charges the BUCK-COM/BUCK+15V voltagesupply to 11.7 volts switch Q1 is off. Thus, an input to NAND gate U4Ais 0, and the output of NAND gate U4A is 1. This output is fed throughdiode D3 and resistors R6 and R7 to the inputs pin 2 of NAND gate U4B,and the output of NAND gate U4B is thus 0. The output of NAND gate U4Bis fed to input pin 2 of NAND gate U4A, thus holding the output of NANDgate U4D high (and holding switch 401 off). Also, at start up the outputof NAND gate U4C is 1 because both its inputs from NAND gate U4B is 0.

[0066] When the bus charges the BUCK-COM/BUCK+15V voltage supply to 11.7volts switch Q1 is turned on, and input pin 9 of NAND gate U4A goeshigh, thus enabling the output of NAND gate U4A to go low, and enablingthe output of NAND gate U4B to go high and the output of NAND gate U4Dto turn on switch 401 (through gates U3). Also, when the output of NANDgate U4A goes to 0, capacitor C3 discharges through resistor R7 (with arelatively long RC time constant). When capacitor C3 has discharged, theoutput of NAND gate U4B goes to 1 causing the output of NAND gate U4D togo 0, turning on buck switch 401.

[0067] The associated circuitry causes the logic to latch until inputpin 8 of NAND gate U4A goes to zero. This happens because when switch401 is on current through inductor L1 increases, turning on a switch Q3through a pair of resistors R11 (2 Kohms) and R10 (100 Kohms) and acapacitor C4 (0.001 μF). When switch Q3 is turned on, input pin 8 ofNAND gate U4A is 0 and the output of NAND gate U4D is 1, causing(eventually) the output of NAND gate U4B to be 0, the output of NANDgate U4C to be 1, and the output of NAND gate U4D to be 1, turning offswitch 401.

[0068] The process of turning switch 401 on and off is repeated, andlimited after the necessary 15V dc bus is created on a pair of outputsPRECOM and PRE+15V. The current through inductor L1 charges a pair ofcapacitors C.13 and C14 (2200 μF). Outputs PRECOM and PRE+15V areconnected across capacitors C14 and C14, thus, when they have charged to+15V, the needed control power is provided. A zener diode D5 preventsthe magnitude of the voltage across outputs PRECOM and PRE+15V fromgetting to high.

[0069] A resistor R13 (1 Kohm), a pair of zener diodes D5 and D2 (6.8V),an opto-isolator OC3, and a resistor R1 (1 Mohm) limit the turning on ofbuck switch 401 when the voltage across outputs PRECOM and PRE+15Vreaches 15 volts. When the voltage drop across diodes D5 and D6 and optoOC3 reaches 15 volts, opto OC3 turns on, pulling up the inputs to NANDgate U4B, turning off switch 401.

[0070] A circuit used to implement aux power supply 106, and a portionof controller 104 that controls aux power supply 106 is shown in FIG. 5.One skilled in the art will readily recognize that the control circuitrymay be located on the same control board as the portion of controller104 that controls preregulator 102 and output circuit 103, or it may belocated remotely therefrom, for example on the PC board for aux powersupply 106.

[0071] Aux power supply 106 includes an inverter in the preferredembodiment, and operates much like a motor drive, or typical AC invertercircuit (the output follows a pattern of high, zero and negative, zero,high, zero, . . . ). The output is, in the preferred embodiment, asynthetic AC, 60 Hz, 575V supply (dependent on magnitude of the 800Vbus). The 575 Volt supply may be transformed to any desired magnitude.Alternatively, the magnitude may be controlled to a lower value byhaving a different bus value, or by bucking the bus value down to adesired level. The regulated level could be preset or user selected.Also, the frequency can be user selected (50 or 60 Hz e.g.) or preset.

[0072] The inverter includes 4 switches 501-505, which are turned on andoff to produce ac power on a pair of outputs AC/2 and AC/1.Specifically, normally switches Q3 and Q4 are on and freewheeling (whenthere is no applied voltage difference across outputs AC/1 and AC/2).AC/1 is made high (and AC/2 low) by-turning switch 502 on and switch 504off. Thus, the conduction path is from the bus, through switch 502, toAC/1 and the load, and then from AC/2 through switch 503 to ground(PRECOM). Conversely, AC/1 is made low (and AC/2 high) by turning switch501 on and switch 503 off. Thus, the conduction path is from the bus,through switch 501, to AC/2 and the load, and then from AC/3 throughswitch 504 to ground (PRECOM).

[0073] The remaining circuitry on FIG. 5 is control circuitry, and ispowered by PRECOM and PRE+15V. The circuitry operates in a conventionalmanner and includes drive circuitry level shifters, current limiters andan enable circuit.

[0074] The gate drives for the switches operate in a conventionalfashion, and include resistors R16 (10 ohms), R17 (5.11 Kohms), R18 (1Mohms), R19 (22.1 ohms), R20 (10 ohms), R21 (1 Mohms), R22 (5.11 Kohms),R23 (22.1 ohms), R24 (2 Kohms), R25 (2 Kohms), R26 (2 Kohms), R27 (2Kohms), R28 (20 Kohms), R29 (20 Kohms), R30 (20 Kohms), and R31 (20Kohms), capacitors C6 (100 μF), C7 (0.1 μF), C10 (100 μF), C11 (0.1 μF),switches Q6, Q7, Q8, Q9, Q10 and Q11, diodes D61 and D7, andopto-isolators OC1 and OC2.

[0075] Latch circuitry current limits each cycle, and operates in aconventional fashion. The latch circuitry includes level shifter U1A(40109), gates U2A, U2B, U2C, U2D, resistors R32 (22.1 Kohms), R33 (22.1Kohms), R34 (20 Kohms), R35 (20 Kohms), R36 (3.01 Kohms), R37 (5.11Kohms), R38 (16 Kohms), R39 (1 Kohms) and R40 (20 Kohms), a capacitorC15 (0.000 μF) and a pair of switches Q12 and Q13. A pair of levelshifters U1B and U1C (40109) are also provided.

[0076] An enable circuit includes opto-isolator OC4, resistors R41 (1Mohms) and R42 (20 Kohms), and capacitor C16 (0.1 μF). A voltageregulator circuit includes voltage regulator VR1, capacitor C18 (0.1μF), capacitor C17 (0.1 μF) and regulator VR1, and produces a regulated+5V supply form the +15V supply generated by the buck regulator.

[0077] A timing circuit sets the clock-for the control circuitry and auxfrequency. The timing circuitry includes a microprocessor MPU1,capacitor C19 (22 μF) and capacitor C20 (22 μf), a crystal oscillator Y1(4.096 MHz), and a level shifter U1D.

[0078] These components cooperate in a known manner to produce thedesired 575V ac, 60 Hz output. As stated above, the circuit could bemodified to allow the user to select the voltage magnitude and/orfrequency.

[0079] Numerous modifications may be made to the present invention whichstill fall within the intended scope hereof. Thus, it should be apparentthat there has been provided in accordance with the present invention amethod and apparatus for providing welding type power from any typicalinput voltage or frequency that fully satisfies the objectives andadvantages set forth above. Although the invention has been described inconjunction with specific embodiments thereof, it is evident that manyalternatives, modifications and variations will be apparent to thoseskilled in the art. Accordingly, it is intended to embrace all suchalternatives, modifications and variations that fall within the spiritand broad scope of the appended claims.

1. A welding type power source capable of receiving a range of inputvoltages and frequencies, comprising: an input circuit configured toreceive an input power signal having an input frequency and an inputmagnitude and provide a first signal having a magnitude responsive tothe input magnitude; a preregulator configured to receive the firstsignal and provide a dc second signal having a preregulator magnitudeindependent of the input magnitude; an output circuit configured toreceive the dc second signal and provide a welding type output powersignal having an output frequency independent of the input frequency andhaving an output voltage independent of the input voltage; apreregulator controller, connected to the preregulator, having a powerfactor correction circuit, and further having a controller power input;and a control power circuit configured to receive the dc second signaland provide a control power signal to the controller power input,wherein the controller power signal has a control power magnitudeindependent of the input magnitude and a control frequency independentof the input frequency.
 2. The apparatus of claim 1, wherein the inputcircuit includes a rectifier.
 3. The apparatus of claim 1, wherein thepreregulator magnitude is greater than the first magnitude.
 4. Theapparatus of claim 3, wherein the preregulator includes a boostconverter.
 5. The apparatus of claim 4, wherein the boost converterincludes a slow voltage switched switch and a slow current switchedswitch.
 6. The apparatus of claim 3, wherein the output circuit includesan inverter.
 7. The apparatus of claim 3 wherein the output circuitincludes a switched snubber.
 8. The apparatus of claim 3, wherein thepreregulator magnitude is greater than the control power magnitude. 9.The apparatus of claim 3 wherein the control power circuit includes abuck converter.
 10. (Cancelled).
 11. A method of providing welding typepower from a range of input voltages and frequencies, comprising:receiving an input power signal having an input frequency and an inputmagnitude; providing a first signal having a magnitude responsive to theinput magnitude; converting and power factor correcting, by controllinga switch, the first signal into a dc second signal having a secondmagnitude independent of the input magnitude; providing an output powersignal derived from the dc second signal, wherein the output powersignal is a welding type output and has an output frequency independentof the input frequency and further has an output voltage independent ofthe input voltage; and converting the dc second signal into controlpower, wherein the control power has a control power magnitudeindependent of the input magnitude.
 12. The method of claim 11, whereinproviding a first signal includes rectifying an ac signal.
 13. Themethod of claim 11, wherein the second magnitude is greater than thefirst magnitude.
 14. The method of claim 13, wherein converting thefirst signal into a dc second signal includes boost converting the firstsignal.
 15. The method of claim 13, wherein boost converting the firstsignal includes a slow voltage switching and slow current switching aswitch.
 16. The method of claim 13, wherein providing an output powersignal includes inverting the dc second signal.
 17. The method of claim13 wherein inverting the dc second signal includes switching a snubber.18. The method of claim 13, wherein the second magnitude is greater thanthe control power magnitude.
 19. The method of claim 13 whereinconverting the dc second signal into control power includes buckconverting the dc second signal.
 20. (Cancelled).
 21. A welding typepower source capable of receiving a range of input voltages andfrequencies, comprising: input means for receiving an input power signalhaving an input frequency and an input magnitude and for providing afirst signal having a magnitude responsive to the input magnitude;converting means for converting, and power factor correcting bycontrolling a switch, the first signal into a dc second signal having amagnitude independent of the input magnitude, wherein the convertingmeans is connected to receive the first signal; means for providing awelding type output power signal derived from the dc second signal,wherein the output power signal and has an output frequency independentof the input frequency and further has an output voltage independent ofthe input voltage, and wherein the means for providing an output powersignal is disposed to receive the dc second signal; means for convertingthe dc second signal into control power, wherein the control power has acontrol power magnitude independent of the input magnitude.
 22. Theapparatus of claim 21, wherein the first means includes means forrectifying an ac signal.
 23. The apparatus of claim 22, wherein theconvertor magnitude is greater than the first magnitude.
 24. Theapparatus of claim 23, wherein the converting means includes means forboost converting the first signal.
 25. The apparatus of claim 24,wherein the means for boost converting includes means for slow voltageswitching and slow current switching a switch.
 26. The apparatus ofclaim 25, wherein the means for providing an output power signalincludes means for inverting the dc second signal.
 27. The apparatus ofclaim 26 wherein the means for inverting includes means for switching asnubber.
 28. The apparatus of claim 27, wherein the converter magnitudeis greater than the control power magnitude.
 29. The apparatus of claim28 wherein the means for converting the dc second signal into controlpower includes means for buck converting the dc second signal.
 30. Awelding type power source capable of receiving a range of input voltagesand frequencies, comprising: a dc bus; an output circuit configured,having a control input and to receive the dc bus and provide a weldingtype output power signal having an output frequency independent of theinput frequency and having an output voltage independent of the inputvoltage; a controller, including a power factor correction circuit,connected to the control input and further having a controller powerinput; and a control power circuit configured to receive the dc bus andprovide a control power signal to the controller power input.
 31. Theapparatus of claim 30, wherein the output circuit includes an inverter.32. The apparatus of claim 31, wherein the output circuit includes aswitched snubber.
 33. The apparatus of claim 30, wherein the dc bus hasa magnitude is greater than a magnitude of the control power signal. 34.The apparatus of claim 30 wherein the control power circuit includes abuck converter. 35-36. (Cancelled).
 37. A welding type power sourcecapable of receiving a range of input voltages and frequencies,comprising: an input circuit configured to receive an input power signalhaving an input frequency and an input magnitude and provide a firstsignal having a magnitude responsive to the input magnitude; apreregulator configured to receive the first signal and provide a dcsecond signal having a preregulator magnitude independent of the inputmagnitude; an output circuit configured to receive the dc second signaland provide a welding type output power signal having an outputfrequency independent of the input frequency and having an outputvoltage independent of the input voltage; a preregulator controller,connected to the preregulator, and further having a controller powerinput; and a control power circuit configured to receive the dc secondsignal and provide a control power signal to the controller power input,wherein the controller power signal has a control power magnitudeindependent of the input magnitude and a control frequency independentof the input frequency, without reconfiguring the control power circuit.38. The apparatus of claim 37, wherein the input circuit includes arectifier.
 39. The apparatus of claim 37, wherein the preregulatormagnitude is greater than the first magnitude.
 40. The apparatus ofclaim 39, wherein the preregulator includes a boost converter.
 41. Theapparatus of claim 40, wherein the boost converter includes a slowvoltage switched switch and a slow current switched switch.
 42. Theapparatus of claim 39, wherein the output circuit includes an inverter.43. The apparatus of claim 39 wherein the output circuit includes aswitched snubber.
 44. The apparatus of claim 39, wherein thepreregulator magnitude is greater than the control power magnitude. 45.The apparatus of claim 39 wherein the control power circuit includes abuck converter.
 46. A method of providing welding type power from arange of input voltages and frequencies, comprising: receiving an inputpower signal having an input frequency and an input magnitude; providinga first signal having a magnitude responsive to the input magnitude;converting the first signal into a dc second signal having a secondmagnitude independent of the input magnitude; providing an output powersignal derived from the dc second signal, wherein the output powersignal is a welding type output and has an output frequency independentof the input frequency and further has an output voltage independent ofthe input voltage; and converting the dc second signal into controlpower, without reconfiguring a control power circuit, wherein thecontrol power has a control power magnitude independent of the inputmagnitude.
 47. The method of claim 46, wherein providing a first signalincludes rectifying an ac signal.
 48. The method of claim 46, whereinthe second magnitude is greater than the first magnitude.
 49. The methodof claim 48, wherein converting the first signal into a dc second signalincludes boost converting the first signal.
 50. The method of claim 48,wherein boost converting the first signal includes a slow voltageswitching and slow current switching a switch.
 51. The method of claim48, wherein providing an output power signal includes inverting the dcsecond signal.
 52. The method of claim 48, wherein inverting the dcsecond signal includes switching a snubber.
 53. The method of claim 48,wherein the second magnitude is greater than the control powermagnitude.
 54. The method of claim 48, wherein converting the dc secondsignal into control power includes buck converting the dc second signal.55. A welding type power source capable of receiving a range of inputvoltages and frequencies, comprising: input means for receiving an inputpower signal having an input frequency and an input magnitude and forproviding a first signal having a magnitude responsive to the inputmagnitude; converting means for converting the first signal into a dcsecond signal having a magnitude independent of the input magnitude,wherein the converting means is connected to receive the first signal;means for providing a welding type output power signal derived from thedc second signal, wherein the output power signal and has an outputfrequency independent of the input frequency and further has an outputvoltage independent of the input voltage, and wherein the means forproviding an output power signal is disposed to receive the dc secondsignal; means for converting the dc second signal into control power,without reconfiguring, wherein the control power has a control powermagnitude independent of the input magnitude.
 56. The apparatus of claim55, wherein the first means includes means for rectifying an ac signal.57. The apparatus of claim 56, wherein the convertor magnitude isgreater than the first magnitude.
 58. The apparatus of claim 57, whereinthe converting means includes means for boost converting the firstsignal.
 59. The apparatus of claim 58, wherein the means for boostconverting includes means for slow voltage switching and slow currentswitching a switch.
 60. The apparatus of claim 59, wherein the means forproviding an output power signal includes means for inverting the dcsecond signal.
 61. The apparatus of claim 60, wherein the means forinverting includes means for switching a snubber.
 62. The apparatus ofclaim 61, wherein the converter magnitude is greater than the controlpower magnitude.
 63. The apparatus of claim 62 wherein the means forconverting the dc second signal into control power includes means forbuck converting the dc second signal.
 64. A welding type power sourcecapable of receiving a range of input voltages and frequencies,comprising: an input circuit configured to receive an input power signalhaving an input frequency and an input magnitude and provide a firstsignal having a magnitude responsive to the input magnitude; apreregulator configured to receive the first signal and provide a dcsecond signal having a preregulator magnitude independent of the inputmagnitude; an output circuit configured to receive the dc second signaland provide a welding type output power signal having an outputfrequency independent of the input frequency and having an outputvoltage independent of the input voltage; a preregulator controller,connected to the preregulator, and further having a controller powerinput; a control power circuit configured to receive the dc secondsignal and provide a control power signal to the controller power input,wherein the controller power signal has a control power magnitudeindependent of the input magnitude and a control frequency independentof the input frequency; and an aux power circuit configured to receivethe dc second signal and provide a synthetic AC aux signal havingmagnitude independent of the input magnitude and a frequency independentof the input frequency.
 65. The apparatus of claim 64, wherein the inputcircuit includes a rectifier.
 66. The apparatus of claim 64, wherein thepreregulator magnitude is greater than the first magnitude.
 67. Theapparatus of claim 66, wherein the preregulator includes a boostconverter.
 68. The apparatus of claim 67, wherein the boost converterincludes a slow voltage switched switch and a slow current switchedswitch.
 69. The apparatus of claim 67, wherein the output circuitincludes an inverter.
 70. The apparatus of claim 67, wherein the outputcircuit includes a switched snubber.
 71. The apparatus of claim 66,wherein the preregulator magnitude is greater than the control powermagnitude.
 72. The apparatus of claim 66 wherein the control powercircuit includes a buck converter.
 73. A method of providing weldingtype power from a range of input voltages and frequencies, comprising:receiving an input power signal having an input frequency and an inputmagnitude; providing a first signal having a magnitude responsive to theinput magnitude; converting the first signal into a dc second signalhaving a second magnitude independent of the input magnitude; providingan output power signal derived from the dc second signal, wherein theoutput power signal is a welding type output and has an output frequencyindependent of the input frequency and further has an output voltageindependent of the input voltage; converting the dc second signal intocontrol power, wherein the control power has a control power magnitudeindependent of the input magnitude; and inverting the dc second signalinto synthetic AC aux power, wherein the aux power has a control powermagnitude independent of the input magnitude.
 74. The method of claim73, wherein providing a first signal includes rectifying an ac signal.75. The method of claim 73, wherein the second magnitude is greater thanthe first magnitude.
 76. The method of claim 75, wherein converting thefirst signal into a dc second signal includes boost converting the firstsignal.
 77. The method of claim 75, wherein boost converting the firstsignal includes a slow voltage switching and slow current switching aswitch.
 78. The method of claim 75, wherein providing an output powersignal includes inverting the dc second signal.
 79. The method of claim75, wherein inverting the dc second signal includes switching a snubber.80. The method of claim 75, wherein the second magnitude is greater thanthe control power magnitude.
 81. The method of claim 75, whereinconverting the dc second signal into control power includes buckconverting the dc second signal.
 82. A method of providing welding typepower from a range of input voltages and frequencies, comprising:rectifying an input power signal having an input frequency and an inputmagnitude to provide a rectified signal having a rectified magnituderesponsive to the input magnitude; boost converting, including slowvoltage switching and slow current switching, the rectified signal toprovide a boost dc signal having a boost magnitude greater than andindependent of the rectified input magnitude; inverting, includingswitching a snubber, the dc second signal to provide a welding typepower output having an output frequency independent of the inputfrequency and having an output voltage independent of the rectifiedmagnitude; converting the boost dc signal to provide a control powersignal, wherein the control power signal has a control power magnitudeless than and independent of the boost magnitude, and a controlfrequency independent of the input frequency; and inverting the boost dcsignal to provide a synthetic AC aux power signal, wherein the aux powersignal has a magnitude less than and independent of the boost magnitude,and a frequency independent of the input frequency.
 83. A welding typepower source capable of receiving a range of input voltages andfrequencies, comprising: input means for receiving an input power signalhaving an input frequency and an input magnitude and for providing afirst signal having a magnitude responsive to the input magnitude;converting means for converting the first signal into a dc second signalhaving a magnitude independent of the input magnitude, wherein theconverting means is connected to receive the first signal; means forproviding a welding type output power signal derived from the dc secondsignal, wherein the output power signal and has an output frequencyindependent of the input frequency and further has an output voltageindependent of the input voltage, and wherein the means for providing anoutput power signal is disposed to receive the dc second signal; meansfor converting the dc second signal into control power, wherein thecontrol power has a control power magnitude independent of the inputmagnitude; and means for inverting the dc second signal into syntheticAC aux power, wherein the aux power has a control power magnitudeindependent of the input magnitude.
 84. The apparatus of claim 83,wherein the first means includes means for rectifying an ac signal. 85.The apparatus of claim 84, wherein the convertor magnitude is greaterthan the first magnitude.
 86. The apparatus of claim 85, wherein theconverting means includes means for boost converting the first signal.87. The apparatus of claim 80, wherein the means for boost convertingincludes means for slow voltage switching and slow current switching aswitch.
 88. The apparatus of claim 87, wherein the means for providingan output power signal includes means for inverting the dc secondsignal.
 89. The apparatus of claim 88 wherein the means for invertingincludes means for switching a snubber.
 90. The apparatus of claim 89,wherein the converter magnitude is greater than the control powermagnitude.
 91. The apparatus of claim 90, wherein the means forconverting the dc second signal into control power includes means forbuck converting the dc second signal.
 92. A welding type power sourcecapable of receiving a range of input voltages and frequencies,comprising: a dc bus; an output circuit configured, having a controlinput and to receive the dc bus and provide a welding type output powersignal having an output frequency independent of the input frequency andhaving an output voltage independent of the input voltage; a controller,connected to the control input and further having a controller powerinput; a control power circuit configured to receive the dc bus andprovide a control power signal to the controller power input; and an auxpower circuit configured to invert the dc bus and provide synthetic ACaux power signal.
 93. The apparatus of claim 92, wherein the outputcircuit includes an inverter.
 94. The apparatus of claim 93, wherein theoutput circuit includes a switched snubber.
 95. The apparatus of claim92, wherein the dc bus has a magnitude is greater than a magnitude ofthe control power signal.
 96. The apparatus of claim 92 wherein thecontrol power circuit includes a buck converter.
 97. A method ofproviding welding type power from a range of input voltages andfrequencies, comprising: receiving a dc bus having a dc magnitude;providing an output power signal derived from the dc bus, wherein theoutput power signal is a welding type output; and converting the dc businto control power, wherein the control power has a control powermagnitude independent of the dc magnitude; providing the control powerto a controller configured to control the output power; and invertingthe dc bus into synthetic AC aux power.
 98. A method of starting toprovide welding type power from a range of input voltages andfrequencies, comprising: receiving an input power signal having an inputfrequency and an input magnitude; providing a first dc signal having afirst dc magnitude responsive to the input magnitude; deriving a seconddc voltage having a second dc magnitude less than the first dcmagnitude; controlling a control converter with the second dc voltage toproduce a control dc voltage; controlling an output converter with thecontrol dc voltage to produce an output signal; and inverting the seconddc voltage to produce a synthetic AC aux signal.